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We demonstrate a muW-level broadly tunable THz source based on parametric down-conversion in orientation-patterned GaAs pumped by femtosecond pulses from a Tm-doped fiber laser. Generated THz powers should be scalable to mW-levels with this approach.
We investigated many-body and radiative coupling effects on intersubband Rabi oscillations in a multiple quantum well system. Under certain conditions, radiative coupling is the dominating effect, yielding distinctively different excitation behaviors in the wells.
Experimental studies of the electron and hole concentration dynamics in the barrier of GaSb-based type-II quantum-well (QW) heterostructures was performed. Difference between electron and hole relaxation rates is explained by corresponding QW carrier confinement energies.
The gain and index dynamics of a QD amplifier operating at 1.55 mum are characterized via heterodyne pump-probe measurements with 150 fs resolution. A 13 ps gain recovery time was found, promising for all-optical signal processing.
The spectral width of terahertz emission from ion-implanted terahertz emitters increases with ion damage, owing to ultrafast carrier capture. Carrier dynamics simulations reinforce these findings. Optical-pump, terahertz-probe experiments confirm the sub-picosecond lifetimes of these materials.
The spin relaxation within the radiative doublet of the exciton ground state in InAs/GaAs quantum dots is studied via ultrafast spectral hole burning spectroscopy. A biexcitonic resonance emerges due to relaxation of the exciton spin.
The feasibility of using femtosecond laser micro-machining to create Gallium Arsenide (GaAs) quasi-phasematched devices from single GaAs wafers is investigated. We describe machining of the structure and details of the machining quality achievable in GaAs.
We demonstrate the picosecond switching in 1D AlGaAs photonic crystal waveguides. We show the decay times vary with the structure parameters demonstrating excellent potential for ultrafast nonlinear switches with a controllable recovery time.
The role of polarons in the quantum kinetics of carrier-phonon interaction is emphasized. Scattering processes involving polarons allow ultrafast relaxation even if the phonon energy is not resonant with the electronic transitions.
Ultrafast optical bistability is demonstrated at 1550 nm in an InP-based two-dimensional photonic crystal distributed resonator. A low intensity threshold of 4 kW/cm2 is observed, with a contrast of 65% between the high and low reflectivity states.
We present time-resolved reflectivity spectra of optically, homogeneously switched photonic crystals. We observe large, ultrafast shifts of stopbands of GaAs/AlAs multilayer structures as well as in the photonic bandgap range of 3D Si inverse opals.
Ballistic pure spin currents generated via quantum interference in the absorption of femtosecond pulses are demonstrated to produce transverse ballistic Hall pure charge currents and vice versa via spin-dependent asymmetric scattering processes.
Femtosecond two-color pump-probe experiments on intersubband absorption spectra of electrons in a GaN/AlN superlattice show distinct spectral holes unraveling both the homogeneous broadening contribution and the underlying optical phonon progression.
Spatio-temporal dynamics of coherent exciton-polariton populations in semiconductor microcavities shows a rich ultrafast behaviour that presages many of the features of coherent matter condensates. For condensates at room temperature the response is necessarily ultrafast.
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